11978521 has 3 divisors (see below), whose sum is σ = 11981983.
Its totient is φ = 11975060.
The previous prime is 11978507. The next prime is 11978539. The reversal of 11978521 is 12587911.
It is a happy number.
The square root of 11978521 is 3461.
It is a perfect power (a square), and thus also a powerful number.
It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12587911 = 7 ⋅1798273.
It can be written as a sum of positive squares in only one way, i.e., 2368521 + 9610000 = 1539^2 + 3100^2
It is not a de Polignac number, because 11978521 - 211 = 11976473 is a prime.
It is a Duffinian number.
It is not an unprimeable number, because it can be changed into a prime (11978581) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (13) of ones.
It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 1731 + ... + 5191.
Almost surely, 211978521 is an apocalyptic number.
11978521 is the 3461-st square number.
11978521 is the 1731-st centered octagonal number.
It is an amenable number.
11978521 is a deficient number, since it is larger than the sum of its proper divisors (3462).
11978521 is an frugal number, since it uses more digits than its factorization.
11978521 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 6922 (or 3461 counting only the distinct ones).
The product of its digits is 5040, while the sum is 34.
The cubic root of 11978521 is about 228.8061707242.
The spelling of 11978521 in words is "eleven million, nine hundred seventy-eight thousand, five hundred twenty-one".